The present invention relates to a device for winding up a textile yarn onto a wind-up support or spool of appropriate shape (cylindrical, conical and the like) which rests against a drive cylinder.
It is well known to wind up a yarn on a tubular wind-up support or spool. Essentially two types of devices for gripping the wind-up support are known.
The first type of known wind-up spool gripping device consists of a mandrel which passes through the spool over its entire length and possesses clamping elements which exert radial forces so as to immobilize or engage the spool on the mandrel. It has been found that an overhanging mounting on a pivot arm facilitates positioning and removal of the wind-up spool. However, this first type of arrangement is very expensive to produce in the case of such overhanging mounting on a pivoting arm.
The second type of known wind-up spool gripping device consists of a pair of rotating and coaxial gripping cheek-plates, each of which acts on one end of the tubular spool. These cheek-plates are mounted by means of bearings at the end of a pivotable stirrup. This stirrup is formed by two arms with parallel axes. One of the arms is articulated so as to allow the disengagement and engagement of the wind-up spool, which, thus gripped between the arms, is kept resting against the cheek-plates. The wind-up support or spool is frictionally driven and caused to rotate by means of a drive motor cylinder.
In order to center the spool between the two cheek-plates, the latter are equipped with conventional appropriate centering devices.
In the course of winding-up, it is necessary for the spool, and hence for the bobbin being formed, to be held so as to exert a constant and uniform pressure against the drive cylinder.
As a result of the speed of rotation of the drive cylinder and hence of the spool, the bobbin being formed has a tendency to bounce. This bouncing often causes the formation of a fault on the bobbin, which is known as "facetting", and which, inter alia, causes poor subsequent unwinding of the bobbin and occasionally a break, and premature wear of the mechanical assembly.
Essentially two types of known shock-absorption techniques are used in order to overcome facetting and related problems and disadvantages. The first, called "braking", consists either of friction discs mounted on the body of the stirrup or of hydraulic equipment.
The second type of shock-absorption is called "anti-return". Essentially "anti-return" consists of preventing the bouncing bobbin from falling back on the drive cylinder and does so by means of an anti-return device. For example, an anti-return device may comprise an inclined disc or truncated cone slidable over a rod connected to the framework. This inclined disc or cone has a tendency to reduce the oscillation of the assembly. In practice, this device is complex and costly.
It is also important to control the density of the turns produced in the course of winding-up in order to keep the density as constant as possible. To do this, it is necessary that the pressure of the spool and of the bobbin being formed against the pilot roller be substantially constant. Since, at the start of the winding-up operation, the pressure is low or even zero, a positive pressure is created artificially. This positive pressure diminishes in proportion to the increase in size of the bobbin. When the bobbin reaches a certain diameter, this artificial pressure becomes negative. Here again, in practice, two solutions for compensating the pressure load are used. The first solution consists of a cam and spring system mounted on the body of the stirrup and a roller mounted on the framework. The action of the roller on the cam causes the stirrup to either press down or lift up and thus produces the desired compensation. This solution is generally satisfactory.
The second solution consists of connecting the stirrup by means of a spring to a pivotal axle parallel to the stirrup axle. If the point of attachment is in a straight line with the pivotal axles, the spring, stretched to the maximum, has no effect on the pressure of the coil on the drive cylinder. Before this alignment is reached, its action is positive so as to increase the contact pressure, and after this alignment, it is negative. This device is not very versatile and futhermore is complex to construct in practice.
Leaving out of account the fact that the units which fulfil the functions of shock-absorption, of pressure compensation and of centering are separate, the current winding-up devices are thus complex and delicate.
This is therefore a general object of the present invention to overcome these disadvantages of known devices.
It is a more particular object of the present invention to provide a novel winding-up apparatus having a stirrup which simultaneously fulfills the three functions of centering, pressure compensation and shock-absorption.
It is another object of the present invention to provide a novel winding-up apparatus which is capable of simultaneously controlling the position of the winding-up apparatus, the pressure on the bobbin of a drive roller and the shock on the thread or yarn forming the bobbin which apparatus is simple, economical and strong in construction.
In preferred form an apparatus according to the present invention for winding-up a yarn on a tubular support or spool caused to rotate by tangential contact with a motor drive cylinder comprises a stirrup formed by two arms pivoting about an axle which is firmly fixed to a framework of a machine. These arms have at their free ends two cheek-plates for gripping the support or spool. One of the arms is fixed and the other arm is articulated. A body portion of the stirrup is provided in order to connect the two arms to one another. The body portion is fixedly attached to the fixed arm and is yieldingly attached to the articulated arm.
There is provided a spring mounted on the fixed pivotal axle of the stirrup. This spring presses, on a first side, on a flexible bearing mounted on the same axle and connected to an end of the movable arm.
This spring presses, on the other side, on a plate, one end of which rests on the body of the stirrup while the opposite end forms a cam for a roller fixed relative to the pivotal axle.
In an advantageous embodiment, this device may also comprise a flexible bearing mounted on the pivotal axle of the stirrup and connected to the end of the fixed arm.
In preferred form, the flexible bearings are made of an elastomer.
The manner in which the invention can be practiced and the advantages stemming therefrom will appear more clearly from the description of the embodiment which follows which is given by way of explanation and without implying a limitation and is supported by the attached figures, wherein like reference numerals have been given to like elements.